Every night at 7:30, a chorus of several thousand clicks sweeps the islands of Pemba and Zanzibar with the punctuality of clockwork.

It is the sound of 400,000 islanders turning on and tuning in to Zanzibar television, the first - and just about the only - color television outlet in Africa.

Then, as children fall silent and old men gaze quizzically, 2 1/2 hours of nightly programming begins.

It is one of the paradoxes of Zanzibar, and perhaps its most glaring. For although they have television - there is a set in every village - Zanzibar's people are poor.

The same villages that have TV sets also have shops that stock little more than cooking oil and cigarettes, and sometimes the cooking oil runs short. Until about three months ago, rice, flour and sugar were rationed.

The daily wage for a laborer is the equivalent of about $1.25, and has not changed much despite high inflation.

About 12 per cent of the population on the two islands that make up the former colony of Zanzibar are infected with malarial parasites today, although the disease was almost wiped out here several years ago.

Health care in general is described by one foreigner as "horrible. It's 50 years behind."

The main health care center on Zanzibar is the stark V.I. Lenin Hospital.

"It is a place you go to die," says an islander.

On paper, at least, Zanzibar has been part of Tanzania since 1964, but it has always kept an arm's length of autonomy from the former Tanganyikan mainland. There is evidence that the arm's length is shrinking and that conditions here are improving somewhat, but the simple question remains: Why is there poverty here at all?

Zanzibar's soil bursts with exotic and lucrative crops like cinammon trees, peppercorn vines, citronella plants, carraway bushes, arabica coffee and the ever-present clove trees that have been widely cultivated here since the beginning of the 19th century.

Zanzibar and Pemba grow nearly 80 per cent of the world's clove crop, which brings them $50 million a year in export earnings and enables them to maintain $65 million in hard currency reserves.

A surprisingly small amount of that goes back to the farmers, who end up with about 1 per cent of the $7,120 per long ton that cloves bring on the world market.

The bulk of the money goes instead to pay for meat and dairy imports, projects like the $5-million-a-year color television operation and a sluggish but substantially bureaucracy that should be providing better public services.

One reason it does not is that the 1964 revolution decrimated what used to be one of Africa's better civil service systems. It was saturated with Asians and the much-hated Arabs. In the exnophobia of the revolution, most of the Asians were summarily kicked out and the number of Arabs killed by the predominantly African majority has been estimated as high as 13,000 to 14,000.

Now, 13 years later, the island's 37-member Revolutionary Council has done little to deal with the heart of its civil service problems.

Sheikh Abeid Karume, the iron-handed dictator killed during a 1972 coup attempt, dabbled instead in color television - he thought Africans would not watch black and white - and a large luxury hotel he designed himself, the type of project that does little for the 80 per cent of the people who till the soil.

It was Karume who ended the successful World Health Organization fight against malaria because, he said, only white people could get the disease.

Karume's successor, Aboud Jumbe, is far more polished, intelligent leader who has improved the lot of his people, especially in Pemba, once a virtual slave state to Zanzibar, since it produces 90 per cent of the clove crop.

He, too, has become mired in projects such asn an expensive underwater team that is being trained and equiped to dive off Zanzibar - but for what?

The main problem may be the Revolutionary Council itself. Its members, in many cases former waterfront workers, have carved out the best government jobs for themselves without doing much to make their ministries work.

"They're really conservative," said a Westerner. "At heart, they're all capitalists."

Jumbe does seem to be trying to get the council into line. He has found convenient mainland transfers, or "promotions," for four of the five councillors who dared to challenge him openly, but in return, he has had to yield some of Zanzibar's political autonomy.

While that may help Jumbe and preserve the political stability, it does little to help the average Zanzibari, who is still forced to sell his cloves to the official clove board at the going government price.

Tired of getting a low return for their cloves, many of the farmers have lost interest. Last year, clove harvests dropped from an annual average of 12,000 tons to 7,000. Only increasing world prices keep the export dollars constant.

The official explanation for the drop is that many of the trees are old or diseased, but at this time of year, when they are ripe for harvest, many trees stand laden with cloves that will go unpicked.

The television station, meanwhile, keeps coming on each night promptly at 7:30.

"It is the first color television station to open in Africa," a guide boasts.

It may someday, for lack of money, be the first to close.